[gamegoblin]

"A multistage (or multi-stage) rocket is a rocket that uses two or more stages, each of which contains its own engines and propellant. A tandem or serial stage is mounted on top of another stage; a parallel stage is attached alongside another stage. The result is effectively two or more rockets stacked on top of or attached next to each other. Taken together these are sometimes called a launch vehicle. Two stage rockets are quite common, but rockets with as many as five separate stages have been successfully launched. By jettisoning stages when they run out of propellant, the mass of the remaining rocket is decreased. This staging allows the thrust of the remaining stages to more easily accelerate the rocket to its final speed and height."

https://en.wikipedia.org/wiki/Multistage_rocket

[lutze]

Right, excellent.

Except the first stage doesn't run out of propellant does it, because it has to LAND again. Hence my puzzlement.

I know why multi-stage rockets are used... I'm asking why this rocket needs them, since they solve a problem it doesn't have by design.

[jessriedel]

Rockets don't have stages because they run out of propellant, they have stages so that you don't spend 99% percent of your fuel pushing engines and tanks into orbit which you don't need once you get there.

[jlgreco]

> "they have stages so that you don't spend 99% percent of your fuel pushing engines and tanks into orbit"

In fact you can kinda make a rocket that can reach orbit that doesn't have "stages" but rather jettisons engines themselves. Early Atlas rockets did this: they had one set of fuel tanks but two engines. About two minutes into the flight they would jettison one of the engines.

[nawitus]

Are you saying it should be single-stage-to-orbit? That's currently technologically nearly impossible, even if the rocket doesn't need to land back to Earth.

[nanofortnight]

Not as technologically impossible as you might think: http://www.reactionengines.co.uk/space_skylon.html

[tomelders]

I really don't understand why Skylon isn't getting more coverage.

[schiffern]

>they solve a problem it doesn't have by design.

This is where you're incorrect. Not having to accelerate the empty first stage to orbital speed (and back!) is a huge fuel savings.